ADU rules in Horry County

A detached ADU (a separate structure) is a conditional use in every zoning district where a single-family detached house is permitted, one per parcel, but the lot must be at least twice the district's minimum lot area and the unit must sit at least 20 feet from the house. Because most subdivision lots are platted near the minimum (6,000 square feet in SF6, 7,000 in SF7, 8,500 in SF8.5), a detached unit typically needs 12,000 to 17,000 square feet or more, so the lot-size gate excludes most suburban lots while larger rural and agricultural parcels qualify. Approval itself is administrative (see permit type).

An ADU within the principal dwelling is a conditional use in every district that allows a single-family detached house, needing only the district's normal minimum lot area. It may have its own separate entrance and need not have an interior connection, but it must share a common wall with the main house and may not change the structure's appearance or character (the code says it 'cannot create a duplex'). The conditions are objective and checked by the Zoning Administrator, so the directory treats this as allowed.

Section 925 sets no floor-area limit for an ADU; it requires only that the unit conform to the code's definition of a single-family dwelling unit or a single manufactured home, one ADU per parcel. Size is therefore bounded by the district's general dimensional standards in Table 2-1 (setbacks, 35-foot maximum height in the common SF districts, lot coverage). Detached units also need a lot twice the district minimum and 20 feet of separation from the house.

The principal dwelling must be occupied by the property owner, and the county implements this with an 'Accessory Dwelling Unit Notarized Authorization Letter' in which the owner certifies under notary that they occupy the residence as the primary dwelling. The ordinance phrases it as a standing condition of the conditional use ('is occupied by the owner'), so it reads as an ongoing requirement rather than an at-application test only. South Carolina has no state law limiting owner-occupancy rules.

Section 925 has no ADU parking rule of its own, but it requires the ADU to conform to the definition of a single-family dwelling unit, and the parking table requires 2 spaces per unit for single-family dwellings, mobile homes and duplexes. The MRD district's separate ADU clause (§207(E)(6)) likewise requires 'adequate off-street parking ... per Article VII'. Expect staff to apply 2 spaces per unit; the code does not state an ADU-specific figure, so confirm with Planning and Zoning.

Although the use table labels an ADU a 'conditional use', in Horry County conditional uses are approved by the Zoning Administrator, not a board: §111 says conditional uses 'shall be permitted subject to a determination by the Zoning Administrator or their designee' that they meet the listed standards. There is no public hearing; the owner submits the notarized owner-occupancy letter with the building permit and certificate of zoning compliance. Appeals of the administrator's decision go to the Zoning Board of Appeals (§115).

The zoning ordinance says nothing about who may occupy or rent the ADU; the only tie is that the owner must live in the principal dwelling, which effectively prevents renting both units. Searches of the full Horry County code (Supplement 88 plus pending bank ordinances through Ord. 66-2026) found no short-term rental, vacation rental or transient-rental zoning regime for the unincorporated county, so nightly rental of an ADU is not separately banned or permitted. Rentals to transients owe the county's 0.5 percent local accommodations fee (§19-8) and hospitality fee (§19-6) on top of state accommodations and sales taxes, and operating requires a county business license. The ADU cannot be split off and sold separately as it must stay on the same parcel (one per parcel).